The frequency spectra and modes of natural vibration of turbine rotors

Introduction. The free vibration method is widely applied to detecting internal defects in rod and lamellar structural elements. In this work, it is used to diagnose a rod sample defect consisting in nonparallelism of the rod ends. The possibility of identifying a defect in the form of a bevel of one of the rod butts by the frequency spectrum of free damped longitudinal and transverse vibration after impact actions to the rod side or butt face is considered. Materials and methods. An experimental facility and a method of contact-free recording of the frequency spectrum of the rod natural vibration by its acoustic radiation spectrum are presented. Signs of a defect in the form of a split frequency of the rod transverse vibration are detected. At the same time, the maximum amplitudes of the split frequencies correspond to higher or lower frequencies depending on the face to which the impact is applied. This allows not only determining the presence of a defect in the form of the bevelled butt face, but also establishing its orientation relative to the side rod faces. Results. An approximate theoretical model is suggested. It explains the effect of frequency splitting in the presence of nonparallelism of the rod butts. For this, the frequency spectra of transverse vibration of two rods with lengths equal to the lengths of the smaller and the larger faces of the original rod with the bevel edge are considered. Experiments show that the differences in the natural frequencies of the bending vibration of these rods, which correspond to the same eigenmodes, are consistent with the differences in the split frequencies of the free damped transverse vibrations of the bevelled-face rod. At this, relationship between the split frequency amplitudes allows determining not only the presence of bevelled face, but also its location. Conclusions. The application and development of the method through the analysis of the natural vibration spectrum can lead to creation of remote quality control equipment for rod structural elements.

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Heart Rate Variability, Emotions, and Music

Journal of Psychophysiology ◽

10.1027/0269-8803/a000021 ◽

2010 ◽

Vol 24 (2) ◽

pp. 112-119 ◽

Cited By ~ 9

Author(s):

F. Riganello ◽

A. Candelieri ◽

M. Quintieri ◽

G. Dolce

Keyword(s):

Data Mining ◽

Heart Rate ◽

Heart Rate Variability ◽

Vegetative State ◽

Low Frequency ◽

Emotional Reactions ◽

Heart Beat ◽

Healthy Controls ◽

Frequency Spectra ◽

Emotional Value

The purpose of the study was to identify significant changes in heart rate variability (an emerging descriptor of emotional conditions; HRV) concomitant to complex auditory stimuli with emotional value (music). In healthy controls, traumatic brain injured (TBI) patients, and subjects in the vegetative state (VS) the heart beat was continuously recorded while the subjects were passively listening to each of four music samples of different authorship. The heart rate (parametric and nonparametric) frequency spectra were computed and the spectra descriptors were processed by data-mining procedures. Data-mining sorted the nu_lf (normalized parameter unit of the spectrum low frequency range) as the significant descriptor by which the healthy controls, TBI patients, and VS subjects’ HRV responses to music could be clustered in classes matching those defined by the controls and TBI patients’ subjective reports. These findings promote the potential for HRV to reflect complex emotional stimuli and suggest that residual emotional reactions continue to occur in VS. HRV descriptors and data-mining appear applicable in brain function research in the absence of consciousness.

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Right-Hemisphere Specialization for Contour Grouping

Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie) ◽

10.1027/1618-3169/a000252 ◽

2014 ◽

Vol 61 (5) ◽

pp. 331-339 ◽

Cited By ~ 1

Author(s):

Gregor Volberg

Keyword(s):

Right Hemisphere ◽

Contour Detection ◽

Global Processing ◽

Detection Accuracy ◽

Frequency Spectra ◽

Visual Hemifield ◽

Spatial Frequencies ◽

A Chain ◽

The Right ◽

Hemisphere Specialization

Previous studies often revealed a right-hemisphere specialization for processing the global level of compound visual stimuli. Here we explore whether a similar specialization exists for the detection of intersected contours defined by a chain of local elements. Subjects were presented with arrays of randomly oriented Gabor patches that could contain a global path of collinearly arranged elements in the left or in the right visual hemifield. As expected, the detection accuracy was higher for contours presented to the left visual field/right hemisphere. This difference was absent in two control conditions where the smoothness of the contour was decreased. The results demonstrate that the contour detection, often considered to be driven by lateral coactivation in primary visual cortex, relies on higher-level visual representations that differ between the hemispheres. Furthermore, because contour and non-contour stimuli had the same spatial frequency spectra, the results challenge the view that the right-hemisphere advantage in global processing depends on a specialization for processing low spatial frequencies.

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